It is fair to say that the links below have not been checked since 2007, so please be patient.

1. This link (still working in May 2007) takes you to the Alwaraq.net Home Page, where you can access thousands of other works, including the Kitāb. The text, though complete, is a stripped down, non-critical version of the Hārūn edition. The site is members only and apparently there is a charge for using it now. You can search the texts by word or phrase and block move it into another document. There are also facilities for feedback and comment.
2. This should take you directly to the Kitāb on the Al-Eman site, though there are some pages to work through before finding the actual text of the Kitāb. Again it looks as though it is a stripped down, non-critical version of the Hārūn edition, and you can block move the text into your word-processor. You can also search the text.
3. On http://www.al-mostafa.com/ you can find a searchable plain text of the whole Kitāb in PDF format and presumably (we haven't tried yet) directly downloadable.
There are undoubtedly other sites, and this will be explored in due course. We repeat, however, that none of these is a critical and/or annotated edition.

Georgetown translation:

The University of Georgetown is making a literal English translation of the Kitāb with parallel Arabic text. So far chapters 1-20 have been completed, in three consecutive issues of the Journal of Arabic Linguistics Tradition, starting in 2003. You will have to register as a user if you want to read the journal, but the translation appears in PDF format and can be downloaded.